Metal particle

Abstract

A metal particle which is a non-nucleated, spherical porous material having continuous open pores, and which is formed from dendritic crystals which have grown uniformly outward from the center without requiring a nucleating agent. The metal particle is unlikely to suffer bonding or aggregation of the metal particles and exhibits excellent dispersibility. When the metal particle is used in a conductive composition, such as a conductive paste, a cured product having satisfactory conduction properties can be obtained at a relatively low temperature, making it possible to easily control the specific gravity or resistance.

The invention claimed is: 
     
       1. A silver particle which is a non-nucleated, spherical porous material having continuous open pores and has:
 a volume cumulative particle diameter D 50  of 0.5 to 9 μm as measured by a particle size distribution measurement method using image analysis; 
 a tap density of 1.8 to 4.5 g/cm 3 ; 
 a specific surface area of 2 to 6 m 2 /g as measured by a BET method; and 
 a value K of 3≦K≦15, 
 wherein the value K is determined from a specific surface area SS and a specific surface area BS, and is represented by the following formula (2), 
 wherein the specific surface area SS is represented by the following formula (1), wherein d is a volume cumulative particle diameter D 50  as measured by a particle size distribution measurement method using image analysis and ρ is a theoretical density of the silver particle, and the specific surface area BS is a specific surface area as measured by a BET method:
   SS=6/ρ d   (1)
 
   (SS/ BS )×100= K   (2).
 
 
 
     
     
       2. The silver particle according to  claim 1 , wherein the region SA of void portions obtained by subjecting the image of the cross-section of the silver particle taken by means of a scanning electron microscope, magnified 20,000 times, to image processing satisfies the relationship: 20≦SA≦40. 
     
     
       3. The silver particle according to  claim 1 , wherein, in an image of the silver particle taken by means of a scanning electron microscope, magnified 20,000 times, the morphology of the appearance of the silver particle has an aegagropila form. 
     
     
       4. The silver particle according to  claim 1 , wherein, in an image of the silver particle taken by means of a scanning electron microscope, magnified 10,000 times, the morphology of the cross-section of the silver particle has a non-nucleated coral form. 
     
     
       5. The silver particle according to  claim 1 , wherein the cross-sectional structure of the silver particle taken by means of a scanning electron microscope, magnified 20,000 times, has a structure shown in  FIG. 1 . 
     
     
       6. A conductive composition comprising the silver particle according to  claim 1 , and a resin. 
     
     
       7. The conductive composition according to  claim 6 , wherein the resin is a thermoplastic resin and/or a thermosetting resin. 
     
     
       8. A conductor comprising a cured product obtained by curing the conductive composition according to  claim 6 . 
     
     
       9. An electronic part comprising the conductor according to  claim 8 . 
     
     
       10. The silver particle of  claim 1  obtained by a method comprising the steps of:
 (a) mixing silver nitrate and citric acid in a liquid phase; 
 (b) adding ascorbic acid or an isomer thereof to the resultant mixture from step (a) to deposit silver particles without adding a nucleating agent; 
 (c) drying the deposited silver particles, 
 wherein steps (a) and (b) are carried out at a temperature of 10 to 30° C., and step (c) is carried out at a temperature of 0 to 80° C.